Process and device for controlling a heating element in a motor vehicle

ABSTRACT

A process and a device for controlling a heating element, in particular a glow plug of a self-igniting internal combustion engine, in which the current is allowed to flow through the heating element when a door contact is actuated and another condition is met.

FIELD OF THE INVENTION Prior Art

The present invention relates to a process and a device for controllinga heating element in a motor vehicle, specifically a glow plug in adiesel engine.

BACKGROUND INFORMATION

A conventional process and a device for controlling a heating element ina motor vehicle is described, for example, in German Patent ApplicationNo. 26 59 264, which described a process and a device including a doorcontact that allows current to flow through the glow plug when the doorcontact is actuated.

The disadvantage of this device is that every time the door contact isactuated, in particular, when the door is closed, heating is triggered.This results in a heavy burden being placed on the vehicle battery,since heating is triggered, for example, even when the occupant leavesthe vehicle.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a process and a devicefor controlling a heating element in a motor vehicle to make quickstart-up possible without placing unnecessary burden on the vehiclebattery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of the device according to the presentinvention.

FIGS. 2a, 2b, 2c and 2d shows various signals plotted against time,during the operation of the device according to the present invention.

FIG. 3 shows a flow chart showing a process according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the present invention is explained below usingthe example of a glow plug of a self-igniting internal combustionengine. The process according to the present invention is, however, notlimited to the present application. A similar procedure can also beapplied with other heating elements used in motor vehicles. Furtheradvantageous is the procedure of heating a lambda sensor or a catalystof an externally ignited internal combustion engine. In such case, thelambda sensor or the catalyst is already fully operational when thestart-up process begins, which improves the emission characteristics ofthe internal combustion engine.

FIG. 1 shows the essential elements of the device according to thepresent invention. A heating element 100 is connected to the vehiclebody. The second terminal of heating element 100 is connected to asupply voltage Ubat through a first switching means 110.

Supply voltage Ubat is also connected to a controller 130 through asecond switching means 120 and a third switching means 140. Firstswitching means 110 receives a control signal from controller 130.

First switching means 110 is preferably a relay or an electronic switch,such as a power transistor, activated by controller 130. Secondswitching means 120 is a switch coupled to the ignition lock, and can beactivated by the driver starting the vehicle. The third switch 140 is adoor contact, which can be activated by opening or closing the door. Inparticular, switch 140 is closed when the door is opened.

In an advantageous embodiment, second switching means 120 and thirdswitching means 140 are provided with a delay function. Thus switchingmeans 120 remains closed for a certain delay period TN even after thedriver has actuated the vehicle with the ignition key. The same appliesto third switching means 140; thus, third switches mean 140 also remainsin its closed position for a certain delay period T_(V) after the doorhas been actuated.

Controller 130 activates first switching means 110 depending on thestatus of second switching means 120 and third switching means 140. Thecurrent is allowed to flow through the heating element by actuatingfirst switching means 110.

FIG. 2a-2l show various signals plotted against time. FIG. 2a shows thesignal applied to switching means 120. As long as switching means 120 isclosed, i.e., the ignition is being actuated, this signal is set high.As long as switching means 120 is open, this signal is set low.

FIG. 2b shows the signal of the third switching means 140, plottedagainst the position of the door contact. As long as the switching meansis open, i.e., the door is closed, the signal is set low. As soon as theswitching means is closed, i.e., the door is opened, the signal is sethigh. FIG. 2c shows the supply voltage applied to controller 130,supplied through switching means 120 and 140.

FIG. 2d shows the actuating signal sent by controller 130 to switchingmeans 110. When this signal is set high, first switching means 110allows current to flow through the heating element.

Up to time T1, ignition switch 120 is in its actuated position. Thismeans that the controller is in its normal state. Up to this time Ti,the supply voltage signal shown in FIG. 2c is set high. After the elapseof the delay period T_(N) at time T2, the supply voltage applied tocontroller 130 drops to zero.

At time T3, the driver opens the door to leave the vehicle, with theresult that door contact 140 is actuated and its output signal goes highuntil time T4. From time T3 on, the supply voltage applied to controller130 goes high again, dropping low at time T5 after the elapse of thedelay period T_(V). At this time the driver has probably left thevehicle and closed the door.

During the time period between time T5 and T6, the vehicle is stopped.At time T6, the driver opens the driver-side door with the result thatthe signal on door contact 140 goes high. At the same time, the supplyvoltage applied to controller 130 goes high. After a brief delay period,at time T7 controller 130 supplies a triggering signal to switchingmeans 110. As a result, heating element 100 is supplied with currentbetween time T7 and time T8. This process is referred to as pre-heating.

Preferably the time period between time T7 and T8 is a fixed period oftime, or can be pre-defined as a function of different parameters suchas, for example, the ambient temperature. At time T9, the driver closesthe driver-side door, with the result that the signal on door contact140 goes low. After delay period T_(V), the supply voltage to controller130 also goes low. Delay period TV is preferably selected so that it islonger than the time period between times T7 and T8. This ensures thateven when the door is closed quickly, i.e., time T9 precedes time T8,there is sufficient time to supply current to the heating element.

At time T11 the driver starts by turning on the ignition switch 120 ofthe vehicle. This results in both the signal of ignition lock 120 andsupply voltage 130 go high. Furthermore, at this time T11 switchingmeans 110 can receive current again to execute the normal heating cycle.The internal combustion engine can be started after the completion ofthe heating cycle. Pre-heating considerably reduces the waiting time andthe heating time.

FIG. 3 shows the procedure according to the present invention using aflow chart. At the beginning of the program, a counter T is set to 1 anda counter K is set to 0 in first step 300. A subsequent query 310 checkswhether the signal has gone from high to low on ignition switch 120. Ifthis is not the case, the query is performed again at a later point intime. If such a change has been detected, a storage device K is set to 1in a subsequent step 320. This value indicates that the signal hasdropped from high to low at ignition switch 120. Query 310 detects thatthe engine, i.e. controller 130, have been turned off.

Subsequently, query 330 checks whether a change from high to low hasoccurred on door contact 140. If this is not the case, query 330 isrepeated after a predefined time. If such a drop is detected, step 340follows, where the content of counter T is incremented by 1. Query 330detects whether the driver has left the vehicle.

Next, query 350 checks whether the value of counter T is equal to 3 andwhether counter K has the value 1. If this is not the case, the programis terminated in step 390. If this is the case, counter T is incrementedby 1 in step 360. Query 350 detects whether the driver has re-enteredthe vehicle. Subsequently, in step 370, switch 110 is actuated, allowingcurrent to flow through heating element 100.

Query 380 that follows checks whether the signal at ignition lock 120has gone from low to high. If this is the case, the program ends withstep 390. If this is not the case, query 350 is repeated after apredefined time.

If it is sequentially detected that the ignition switch has been turnedoff, the driver has left the vehicle and later re-entered it, with theseactions occurring in this sequence, it can be assumed that a preheatcycle should be started. The current is allowed to flow in step 370.This means that switch 110 is closed. In one embodiment of the presentinvention, it can also be provided that controller 130 generates asignal showing that the preheat cycle can begin. If this signal ispresent, controller 130 activates switch 110 with a suitable mark-spaceratio.

If not all actions are detected, or the actions are detected in someother sequence or at a higher frequency, the preheat cycle is notstarted.

If the driver behaves in an expected manner, i.e., he leaves thevehicle, then re-enters it later and starts the engine, the start timecan be considerably reduced by immediately starting the preheat cycleafter re-entry.

The preheat cycle is initiated after query 350 only if theshut-off-engine and leave-vehicle actions occur in the predictedsequence.

In the case of a different sequence and/or repeated door contactsignals, the preheat cycle is not started when the door contact isactuated.

I claim:
 1. A method for controlling a heating element in a motorvehicle, comprising the steps of:actuating at least one door contact ofthe motor vehicle; changing a state of an additional member of the motorvehicle, the additional member including an ignition lock member; andproviding a current flow through the heating element to start a preheatcycle when the door contact is actuated and the state of the additionalmember is changed in a predetermined time sequence.
 2. The methodaccording to claim 1, wherein the current flow is provided through theheating element when the door contact is actuated at least twice afterthe state of the ignition lock member has changed.
 3. A method forcontrolling a heating element in a motor vehicle, comprising the stepsof:actuating at least one door contact of the motor vehicle; changing astate of an additional member of the motor vehicle; and providing acurrent flow through the heating element to start a preheat cycle whenthe door contact is actuated and the state of the additional member ischanged in a predetermined time sequence, wherein the heating elementincludes a glow plug of a self-igniting internal combustion engine.
 4. Adevice for controlling a heating element of a motor vehicle,comprising:at least one door contact; an additional switching member,the additional switching member including an ignition lock member; and acontroller for providing a current flow through the heating element whenthe door contact is actuated and a state of the additional switchingmember changes in a predetermined time sequence.
 5. A device forcontrolling a heating element of a motor vehicle, comprising:at leastone door contact; an additional switching member; and a controller forproviding a current flow through the heating element when the doorcontact is actuated and a state of the additional switching memberchanges in a predetermined time sequence;wherein the heating elementincludes a glow plug of a self-igniting internal combustion engine.
 6. Adevice for controlling a heating element of a motor vehicle,comprising:at least one door contact; an additional switching member;and a controller for providing a current flow through the heatingelement when the door contact is actuated and a state of the additionalswitching member changes in a predetermined time sequence;wherein theheating element heats at least one of a lambda sensor and a catalyst.